Drier section of papermaking machine



April 23, 1968 J. BUSS DRIER SECTION OF PAPERMAKING MACHINE Original Filed Sept. 18, 1963 4 Sheets-Sheet 1 April 23, 1968 J. BUSS 3,378,936

DRIER SECTION OF PAPERMAKING MACHINE Original Filed Sept. 18, 1963 4 Sheets-Sheet 2 April 23, 1968 J. BUSS 3,378,936

DRIER SECTION OF PAPERMAKING MACHINE 'Jriginal Filed Sept. 18, 1963 4 Sheets-Sheet 5 lfl April 23, 1968 J. BUSS DRIER SECTION OF PAPERMAKING MACHINE 4 Sheets-Sheet 4 Original Filed Sept. 18, 1963 United States Patent 2 Claims. (Cl. 34116) ABSTRACT OF THE DISCLOSURE An improvement for minimizing paper shrinkage in a paper drying machine for drying a continuous running sheet of paper having an upper row of drier rolls and a lower roll of drier rolls staggered with respect to the rolls of the upper row and a paper sheet passing successively around the drier rolls of the upper and lower rolls, including, a pair of double mesh screens maintained under tension and adapted to firmly contact the top and bottom of the paper sheet and support it throughout substantially the full extent of the drier, the upper row of drier rolls and the lower row of drier rolls being so positioned in relation to each other as to decrease the distance which the paper must travel between rolls to a minimum.

This invention relates to the drier section of a paper making machine, and more particularly, to means for solving a problem which is unique to the papermaking industry, that of maintaining the dimensional stability of paper.

This is a continuation of patent application Ser. No. 309,818 filed on Sept. 18, 1963, and now abandoned.

The dimensional stability of paper is important in connection with many uses in the papermaking industry. For example, where successive impressions are printed on the paper any variation in the dimensions of the paper will result in a poor registration. Similarly, if punch cards are being made, variations in the dimensions of the paper may interfere with the recording of information. The tendency of some paper to curl is partly due to lack of dimensional stability. The wavy edges sometimes seen at the edge of pads or piles of paper is also due to poor dimensional stability.

The extent to which paper expands or contracts as a result of moisture absorption or desorption is largely due to the degree of shrinkage during the paperrnaking operation, and thus is a problem which is not faced in any other industry. Consequently, minimizing the shrinkage which tends to occur during drying has been a longstanding problem, and one to which the present invention has provided the first practical solution. The shrinkage which takes place in the drier section of a paper machine occurs particularly near the edges of the sheet of paper with the consequence that the performance of a particular piece of paper often varies in accordance with whether it is derived from the center or adjacent to the edge of the sheet.

In a conventional drier the drying rolls are arranged in two rows with the rolls of one row being staggered with respect to the rolls of the other row. The sheet is threaded alternately over a roll of the upper row and under a roll of the lower row. There are separate drier felts for the upper and lower rows. Each of these felts is tensioned against the top side of the upper drier rolls and against the under side of the lower drier rolls by felt idler rolls. The sheet is unsupported by any felt when passing back and forth between the upper and lower rows of drier rolls. Most of the shrinkage occurs in this area between the upper and lower rows of drier rolls when there is no adhesion of the sheet to any roll or felt to reduce the shrinkage to a low value.

While it has been previously proposed to feed a sheet of paper between fibrous blankets to inhibit lateral shrinkage, such as shown in US. Patent No. 2,484,676 which issued on Oct. 11, 1949, to Bidwell, the apparatus suggested by Bidwell could not be adapted to a high speed machine, for the use of fibrous blankets would be impractical due to the problem of drying the blankets which become soaked with water. Furthermore the contact between the blankets and the sheet would not be sufficiently firm to be fully effective in restraining shrinkage. Experimentation has established that the use of such felts is not practical because the loss in drying capacity of any given machine would be tremendous due to the insulating qualities of the fibrous felts and the necessary length of drier section would be almost inconceivable, not only from the standpoint of space requirements but also expense. While it is conceivable that an attempt could be made to dry the felts on their return journey, the paper would still not be dry and the drying equipment would not only be costly but would occupy considerable space which in the majority of cases is not available on present day machines.

The present invention is based on the concept of supporting the sheet of paper throughout substantially the full extent of its passage through the drier, between a pair of continuous open mesh screens. These screens are tensioned and are in firm contact with the paper sheet. Therefore, the sheet is substantially restrained from shrinking. The open meshes permit the free release of moisture from the sheet and thereby avoid the problem, which would otherwise have to be faced of drying the felt. Although, in accordance with this invention in its broadest aspect the screen can be a metal wire mesh, the screen should, in accordance with another aspect of the invention, be of a material of low heat conductivity such as nylon or other synthetic fiber. When the Wire screen is continuously in contact with and in registration with the same position on the sheet, wire marking may occur. In the present invention however, this danger of wire marking can be eliminated by using screens of synthetic fiber. An additional advantage of synthetic fiber is that in the case of short drier lengths it can be made in the form of a continuous length without any seam.

In an apparatus in accordance with this invention the conventional felt idler rolls between the drier rolls may be eliminated. In accordance, however, with a further aspect of this invention they may be retained and used to decrease the distance traveled by the sheet between the drier rolls in order to improve the contact of the sheet with the two supporting screens. These also increase the length of travel in the drier section to increase the capacity of the drier. This would not be possible with an ordinary drier felt in that the unsupported sheet would not travel around the idlers.

In the present invention idler rolls are not only used to decrease the distance travelled by thesheet between rolls, but also to control the angle of travel of the web so as to insure closer contact between the paper web and its accompanying screens decreasing the unsupported distance between rolls to a minimum and thereby maximizing the prevention of lateral shrinkage.

In the drawings, which illustrate the preferred embodiments of this invention FIGURE 1 is a schematic elevation view illustrating one embodiment of this invention.

FIGURE 2 is a schematic elevation view illustrating another embodiment of this invention.

FIGURE 3 is an elevation view of one side of the structure shown in FIGURE 2.

FIGURE 4 is an elevation view of the opposite side of the structure shown in FIGURE 2 to that illustrated in FIGURE 3.

FIGURE 5 is a sectional elevation view of the line 5-5 of FIGURES 3 and 4.

Referring now to FIGURE 1 of the drawings, there is illustrated a drier section including an upper row of drying rolls 19a, b, 19c, 10d, lite, 10 Mg, 10h, staggered with respect to a lower row of drying rolls 11a, 11b, 11c, 11d, 11c, 11 11g, and 11h. An upper screen 12 passes around roll 11a, over roll 10a, around roll lib, and in a similar manner over the other rolls of the upper row and around the rolls of the lower row. Screen 12 then passes around take ofi" idler roll 13 and around a series of idler rolls 14a to 14k and then back to roll Ila. Idler rolls 14c and 14h are illustrated as being positioned to act as take-up rolls. Idler roll 14!: provides an adjustment for any looseness after a period of use, while idler roll 14c can be weighted to give a tension of a constant Value; similarly, a lower screen 15 passes around roll 11a and over roll 10a and then around roll 11b and the other rolls, and is then directed by idler rolls 16a to 161 around felt drier roll 17 and then to roll 11a. Roll 16a is positioned to act as a take-up roll for the lower screen. Sheet 18 is sandwiched between screens 12 and 15 at nip 19 and travels through the drier section to its discharge point without at any time having an unsupported length which can shrink to a material extent.

In the alternative embodiment shown in FIGURE 2 there is an upper screen 26 and lower screen 21 between which sheet 22 is sandwiched. The sheet 22 together with the lower portion of screen and the upper portion of screen 21 pass successively around the rolls 23 of a series of lower drier rolls and the rolls 24 of a series of upper drier rolls. However, as the screens and the sheet pass from lower roll 23 to upper roll 24 they travel around idler roll 25 which is located below upper roll 24. Also, as the screens and sheet pass from upper roll 24 to lower roll 23a, they go around idler roll 26 which is located above roll 23a. A series of idler rolls 27 guide screen 20 and a series of idler rolls 2% guide screen 21 in a manner similar to that explained in relation to FIG- URE 1.

Suitable provision is made for supporting and driving the rolls described in FIGURES 1 and 2. This will not be described in detail as conventional structures can be used. The general nature of the structures will be apparent from FIGURES 3, 4 and 5. In FIGURE 3 the supporting structure is provided by sole plate 29 which supports column 30 upon which is mounted beam 31. The shaft 32 of roll 23b is journalled in bearing 33 which is mounted on plate 34. Plate 34 is supported by sole plate 29. A mounting platform 35 is located on column 30 to support the bearing 36 for the shaft 37 of idler roll 25b.

Similarly, platform 38 is provided for mounting the bearing 39 for shaft 40 of idler roll 26b. Platform 38 is secured to beam 31. Bearing 41 is on plate 42 which is in turn on beam 31 to journal shaft 43 of roll 24b.

As illustrated in FIGURES 4 and 5, sprockets such as and 50a are mounted on the roll shafts such as 32 and 32a of the lower row. These sprockets mesh with sprockets such as 51 mounted on the roll shafts and 43 of each of the rolls of the upper row so that all the rolls rotate in synchronism and the rolls of the upper row rotate in a direction counter to that of the lower row of rolls. Suitable drive means are provided such as motor 52 which drives pulley 53. Pulley 53 is connected by belts 54 to pulley 55 which is secured to intersecting sprocket drive 56. Power for driving the drier rolls is transmitted by the intermeshing sprocket drive 56 to two of the central rolls of the drier section. It

is then transmitted by interrneshing sprockets such as 50 and 50a to the remainder of the rolls. A conventional gear reduction unit (not shown) may be used as part of the drive from motor 52. In addition to the advantages previously referred to, an apparatus in accordance with the present invention can readily be used in conjunction with air cap auxiliary driers and other drying aids, including those that tend to disturb or wrinkle the sheet. Such aids materially improve the drying capacity and consequent production of a paper machine. With this invention air caps could be applied to all driers.

Also, an apparatus in accordance with this invention could eliminate stack blocks in driers, drier doctors, felt drying rolls, drier threading, the sheet sticking to driers and the production of fiutr". Another advantage of the apparatus of this invention is that there is an increase in the width of a sheet from a given machine because of the reduction of shrinkage. This also tends to eliminate grainy edges and give better dimensional stability.

It has been found that sometimes after a shutdown driers will tend to rust somewhat and will leave spots on the paper when first started up. In addition, it is known that the sheet will sometimes pick up iron from the drier shell. Even though the particles are quite invisible, they are enough to be a detriment in some kinds of paper, particularly those intended for certain duplicating methods. However, an apparatus in accordance with this invention provides a sheet which is free from iron or iron rust either visible or invisible.

While I have shown the preferred method and means of practicing the present invention it is to be understood that various changes may be made by those skilled in the art without departing from the spirit of the invention as claimed.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. In a paper drier machine for drying a continuous running sheet of paper, having an upper row of drier rolls and a lower row of drier rolls staggered with respect to the rolls of the upper row, and said paper sheet passing successively around the drier rolls of the upper and lower rows, an improvement for minimizing shrinkage in said paper, comprising a pair of open mesh screens maintained under tension and adapted to firmly contact the top and bottom of said paper sheet and support said paper sheet throughout substantially the full extent of the drier, said upper row of drier rolls and said lower row of drier rolls being so positioned in relation to each other as to decrease the distance which the paper must travel between rolls to a minimum, idler roll means poistioned so as to control the angle of travel of said paper sheet so as to insure close contact between it and its accompanying screens, decreasing the unsupported distances between rolls to a minimum and thereby further minimizing the prevention of lateral shrinkage, said idler roll means including a first set of idler rolls positioned between the rolls of the lower row of dr-ier rolls and below the rolls of the upper row of drier rolls and a second set of idler rolls positioned between the rolls of the upper row of drier rolls, and above the rolls of the lower row of drier rolls, said top and bottom screen and said paper sheet supported thereby passing successively around a drier roll of the lower row, over an idler row of said first set, around a drier roll of the upper row, and over an idler row of said second set, said top screen also passing around a third set of idler rolls positioned above the rolls of the upper rows of drier rolls, said third set of idler rolls maintaining said top screen under tension, and said bottom screen also passing around a fourth set of idler rolls positioned below the rolls of the lower row of said drier rows, said fourth set of idler rolls maintaining said bottom screen under tension.

2. A device as defined in claim 1 including means for rotating all the rolls in synchronism and the rolls of the row of rolls.

5 upper row in a direction counter to that of the lower References Cited UNITED STATES PATENTS 2/1916 Meyers 34-118 5/1916 Pope 34-117 X 11/1926 McCorkindale 34116 X 10/1949 Bidwell 34111 6 3,174,228 3/1965 Smith 34114 X 3,250,019 5/1966 Beachler 34-1 17 FOREIGN PATENTS 5,855 1910 Great Britain. 223,104 10/1924 Great Britain.

FREDERICK L. MATTESON, JR., Primary Examiner. A. D. HERRMANN, Assistant Examiner. 

